This invention relates to a method and apparatus for forming long cylindrical metal products constituted by solid or hollow cylindrical metal products, and more particularly to a method and apparatus for reducing, elongating and pre-forming pipes and bars having substantially circular cross-sections.
In today's seamless pipe manufacturing process, pipe rolling is carried out after piercing of a material bloom. In the rolling process, the pierced bloom is reduced and elongated to a pipe having a specified diameter on rolling equipment combining all or some of devices known as an elongator, plug mill, mandrel mill, reeler, sizer, reducer and other units. Because of the lower working efficiency of the individual units, however, conventional rolling equipment has required several to more than ten stands to achieve the desired result, which stands can be installed only at the expense of huge amounts of capital and large areas of space.
Bars are rolled by a rolling mill train comprising roughing, intermediate and finishing stands which add up to from several to more than ten in number, presenting problems similar to those experienced with pipe rolling.
Pipes and bars can be also manufactured by such plastic working methods as extrusion, drawing and forging, but these manufacturing technologies have been developed to the fullest extent and no room is left to achieve any further efficiency improvement.
On the other hand, conventional rolling mills for pipes and bars have entirely different structures. If their essential structures were the same, significant mill cost reduction would be achieved through the use of common or interchangeable parts, simplification of mill design, and reduction of mill varieties. It might also become possible even to reduce, elongate and preform pipes and bars on the same mill.
Such being the case, drastic technical innovation in pipe and bar manufacturing technologies has long been awaited.